WDIO31 PGTW 100900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 02A (BIPARJOY) WARNING 
NR 017//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 17.2N 67.4E
   INITIAL INTENSITY: 85 KTS
   GEOGRAPHIC REFERENCE: 457 NM SOUTH OF KARACHI, PAKISTAN
   MOVEMENT PAST 6 HOURS: NORTHWARD AT 05 KTS
   SIGNIFICANT WAVE HEIGHT: 30 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A PARTIALLY
EXPOSED LOW LEVEL CIRCULATION CENTER (LLCC) AS THE SYSTEM ONCE
AGAIN CONVECTIVELY FALLS APART AND SUCCUMBS TO THE PERSISTENT
EASTERLY SHEAR. WITH NO RECENT MICROWAVE OR SCATTEROMETRY DATA,
ONCE AGAIN SYNTHETIC APERTURE RADAR (SAR) CAME TO THE RESCUE. A
100125Z RADARSAT-2 SAR IMAGE REVEALED A LARGE AND REASONABLY
SYMMETRIC CIRCULATION, BUT THE BIGGEST SURPRISE WAS THE VMAX OF
106KTS. THOUGH EXTREMELY HIGH RESOLUTION, LARGE INCLINATION ANGLES
CAN ADVERSELY AFFECT VMAX ERROR. FURTHER ANALYSIS OF THE SAR DATA
REVEALS THE SOUTHEASTERN QUADRANT WAS THE CLEAR DECIDING FACTOR IN
THE HIGH VMAX RETURN, WITH ALL OTHER QUADRANTS REPORTING MUCH
CLOSER NUMBERS TO THE REMAINING INTENSITY ESTIMATES. WHETHER
CONTAMINATION DUE TO CONVECTION OR A MESOSCALE WIND SURGE EVENT,
THE JTWC INITIAL INTENSITY IS PLACED JUST ABOVE THE REMAINING
REPORTING INTENSITY ESTIMATES. CIMMS ADT, D-PRINT, D-MINT AS WELL
AS ALL AGENCY DVORAK ESTIMATES INDICATE A RANGE OF 77-90KTS. FOR
ALL OF THE ABOVE REASON THE JTWC POSITION AND INTENSITY OF 85KTS IS
ASSESSED WITH MEDIUM CONFIDENCE.

INITIAL WIND RADII BASIS: SAR DATA 

CURRENT STEERING MECHANISM: NORTHERN PERIPHERY OF A NEAR-EQUATORIAL
RIDGE (NER) TO THE SOUTH AND THE WESTERN PERIPHERY OF A NORTH-SOUTH
ORIENTED RIDGE OVER WESTERN INDIA. 


AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T5.0 - 90 KTS
   KNES: T4.5 - 77 KTS
   DEMS: T4.5 - 77 KTS
   CIMSS ADT: 77 KTS AT 100300Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 15-20 KTS
   SST: 31-32 CELSIUS
   OUTFLOW: STRONG WESTWARD

ANALYSIS CONFIDENCE:
   INITIAL POSITION: MEDIUM
   INITIAL INTENSITY: MEDIUM
   INITIAL WIND RADII: MEDIUM

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO
THE FORECAST FROM THE PREVIOUS WARNING.

FORECAST DISCUSSION: TC 02A IS FORECAST TO REMAIN ON A GENERALLY
NORTHWARD TRAJECTORY THROUGH THE FORECAST PERIOD. CURRENTLY IN A
MARGINALLY FAVORABLE ENVIRONMENT CHARACTERIZED BY STRONG UPPER
LEVEL OUTFLOW AND WARM SSTS PARTIALLY OFFSET BY PERSISTENT AND
BUILDING EASTERLY SHEAR. THROUGH TAU 24, 02A MAY ACHIEVE SHORT-TERM
GROWTH IF IT CAN REMAIN CONVECTIVELY COHESIVE WHICH WOULD RESULT IN
INTENSIFICATION TO AROUND 90KTS. AFTER TAU 24, WITH PERSISTENT
VERTICAL WIND SHEAR NOW JOINED BY RAPIDLY DETERIORATING OUTFLOW
ALOFT, 02A WILL GRADUALLY WEAKEN THROUGH THE FORECAST PERIOD. THE
FORECAST TRACK IS ANOTHER MATTER ENTIRELY. AS THE SYSTEM PROGRESSES
POLEWARD, BOTH THE SPREAD IN MODEL SOLUTIONS AND SHORT TERM
VARIABILITY CANNOT BE OVERSTATED. WITH GFS AND ECMWF PROPOSING TWO
VERY DIFFERENT STEERING PATTERNS, THE RESULTING TRACK GUIDANCE IS
BIFURCATED. THE STRENGTH AND EXACT ORIENTATION OF THE STR THAT SETS
UP OVER THE GULF OF OMAN IS PIVOTAL TO THE LONG TERM TRACK
DIRECTION OF 02A.  

MODEL DISCUSSION: AS DISCUSSED ABOVE, NUMERICAL MODELS ARE
INITIALLY IN FAIR AGREEMENT AND IN POOR AGREEMENT THEREAFTER. ECMWF
AND THEIR ENSEMBLE CURVE THE SYSTEM EASTWARD AFTER TAU 72 TOWARD
NEW DELHI WHILE NVGM, GFS, COAMPS-TC AND HWRF CURVE THE SYSTEM
WESTWARD TOWARDS THE GULF OF OMAN. FOR THIS REASON THE INITIAL
TRACK FORECAST IS PLACED INITIALLY WITH MEDIUM CONFIDENCE AND WITH
LOW CONFIDENCE THEREAFTER. RELIABLE MODEL INTENSITY GUIDANCE IS IN
FAIR AGREEMENT WITH ALL MEMBERS SHOWING MARGINAL INTENSIFICATION
AFTER WHICH A GRADUAL WEAKENING WITH THE EXCEPTION OF COAMPS-TC AND
HWRF WHICH INDICATE ANOTHER ROUND OF INTENSIFICATION NEAT TAU 72.
FOR THESE REASONS THE JTWC INTENSITY FORECAST IS PLACED WITH
OVERALL MEDIUM CONFIDENCE.

FORECAST CONFIDENCE:
   TRACK 0 - 72 HR: MEDIUM
   TRACK 72-120 HR: LOW
   INTENSITY 0 - 72 HR: MEDIUM
   INTENSITY 72-120 HR: MEDIUM//
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